Leakproof terminal structure



Aug. 29,1944, R. W. DE MONTE ETAL 'LEAK-PROOF TERMINAL STRUCTURE FiledOct. 20, 1942 R ne 05 MONTE Patented Aug. 29, 1944 2,356,831 mmaoorTERMINAL srancrrmn Robert W. De Monte. Glen Ridge, N. J., and Louis E.Milarta, Hollis, N. Y., assiznors to Bel] Telephone Laboratorles,Incorporated, New York, N. Y., a corporation of New York ApplicationOctober 20, 1942, Serlal No. 462,698

1 Claim.

This invention relates to an electrical terminal and}; method ofconstructing and mounting the terminal on an apertured wall.

The object of the invention is to provide 9. terminal structure andarrangement suitable for use on a casing which must be seaied againstthe outrance of moisture or the escape of oil or other filling materialin the casing.

The terminal when constructed and assembled according to the inventionwill be suitable for use, for instance, on transformer casings even whenthecasing is subjected to various moisture conditions containing saltand when the casing is subjected to Wide ranges of temperature changes.The construction and arrangement may also be used on oil-fllled casingsand terminais mounted thereon.

In the drawing the single figure shown thereln is a view partly insection of a portion of a casing and the terminal mounted on andextending through an apertured wall in the casing. It will be understoodthat the casing may contain a transformer or some other electricalapparatus (not shown) The casing 2 may be of any desired shape or formbut is shown merely for the purpose et illustrating the invention ascomprising 8. cuplike body 3 and a. cover 4 which serves as a topclosure Ior the upper end of the body 3. The cover 4 is secured to thebody 3 in any suitable marmot to provide a leaf-prooi Joint between thecasinz parts. The body 3 and the cover 4 may -be made, for instance, etsheet metal and the body and cover may be welded or soldered tozether asshown at 5 to provide a leak-prooi Joint betWee1ithe parts. The cover 4is apertured' gitudinally through an insulating bushing Il which extendsthrough the aperture I in the cover 4. The conducting rod n lamale-threaded on its lower and l2 to receive a nut II and in providedwith an integral fiance I4 near its upper end II. The bushing Il is madeof ceramic'material and has a frusto-conical upper portion I! portion [6s 01. larger diameter than the aperture S. A cylindricai tubular portion11 of the insulating bushing Il extends through the aperture 6 and for aconsiderable distance below the cover 4, the portion H being of slightlysmaller outside diameter than the aperture 6. A tubular collar 18 ofceramic material is telescoped over the lower end of the portion Il.

Insulating washers MI, 20, 2l, 22 and 23 are provided in the terminal 1to partly seal parts of the structure pressed into engagement with otherParts when the terminal 1 is assembled and mounted on the cover 4. Thewashers l9, 20, 2l, 22 and 23 are made of flbrous insulating materialand are somewhat compressea when the terminal 1 is assembled and mountedin place. Hempwood pulp has been found to be a suitable materiall forthe washers above mentioned. We do not desire to be limited to the useof this particular materlal, however, since other fibrous insulttingmaterials are in some cases found suitable for the purpose. The washerl9 is placed on the conducting rod H) and so that it is disposedbetweenthe flange I4 and the top oi the insulating bushing II. Thewasher 20 is placed on the portion I! of the insulating bushing H and sothat it: is disposed between the lower and of the trusto-conical portionl6 and the upper surface oi! the cover 4. The washers 2l, 22 and 23 areplaced on the portion ll of the insulating bushing il in the order namedand so that they are located between the upper and of the collar Il andthe undersuriace of the cover 4. The washer 2l 15 nearest to the cover4. A pile-up of washers 24, 2l, 26 and a look washer 21 all made oiconducting material are placed in the order named on the. conducting rodIl! and are held thereon by means 01 the nut in. The washer 24 is etlarxer diameter than the inside diameter of the collar Il and isdisposed against the lower end 01 the collar la. When the nut H 1stightened on the rod I, the parts of the terminal 1 are drawn intoclosely assembled condition and the washers II, 20, 21, 22 and 28 aresomcwhat compressed. The washer 25 is provided with an angularlydisposed apertured ear portion 28 so that a conductor wire (not shown)may be electrically connected to the terminal 1. The conductor wirementloned niay form an electrical connectlon between the terminal 1 andan electrical device located in the casing 2.

In assembfing the terminal 1 above described and in mountinx theterminal on the casing 2 a particular technique is Io1lowed and amoisturelocated above the cover 4 and the base of the proot sealinzcompound 20 is applied to certain of the parts make the structuresleak-proof at certain points where parts of the terminal are pressedtogether and where the terminal extends through the cover 4. Thetechnique above mentioned is as follows:

(1) The coatings 8 and 9 on the cover 4 are abraded or rubbed down toform seating surfaces for the washers 20 and H, the seating surfacesbeing formed only in the coatings I and 9. The seating surfaces shouldnot contain grooves extending radiaily of the aperture and may be formedby circularly rubbing or machining the coatings 8 and 9 around theaperture in the casing. The seating surfaces formed are cleaned withcarbon trachloride or other suitable cleaning fiuid and then thoroughlydried.

(2) The under surface of the flange M and immediately adjacent portionof the conducting rod l0. the top and the lower surface of thefrustoconical portion Hi of the insulating bushing Il are cleaned withcarbnn tetrachloride or other suitable cleaning fluid and thenthoroughly dried.

(3) The washers IS, 20 and 2l are cleaned with a suitable claning fluid.These parts are evendried at a temperature of 140 F. to 160 F. for aboutfour hurs. The washers la, 20 and 2l should then be stored in adesiccator or equivalent containing calcium chloride until required forass mbling in the terminal when they should be removed and handled withtweezers or other pick-up tool to insure cleanliness of the washersuntil applied in the terminal assembly.

(4:) A coat of moisture-proof seaiing compound 28 is applied to theseats formed in,the coatings I and 8 on the cover 4, the sealingcompound beinz of such character that it will balte to substantiailypermanent hardness when subjected to a temperature of between 220 F. and240 F. for twelve to sixteen hours.

(5) A coat of the above-mentioned sealing compound is applied to theunder surface of the flange H and the immediately adjacent portion ofthe conducting rod III.

(6) A coat of the sea1ing compound is applied to the top and lower partof the frusto-conicai portion IS et the insulating bushing il.

(7) The washers IS, and M are dipped in the sealine compound andassembled in the terminal 1 in condition for clamping the parts togetherby operation 01 the nut l3, the parts coated with the seaiing compoundbeing assembled while the seaiing compound is in a tacky condition.

(8) While the sealing compound is in a tackv condition the nut li on therod I0 is tightened to hold the parts in tightly assembled condition.

(9) The terminal 1 and the cover 4 are baked at a temperature of between220 F. and 240 F. for from fourteen to sixteen hours.

(10) The nut Il is still further tightened on the rod Il) while theparts are still at about the temperature above mentioned.

(11) A coat of the sea1lng compound is applied to the outer edge of thefiange l4, the outer surface of the washer I! and the outer surface ofthe upper part of the portion IS et the insulating bushing l l.

(12) A coat of the sealing compound is applied to the outer edze of thewasher 20 and so that the coat of sealing compound extends over theoutside of the lower part f the portion I6 and also over the nearbyportions of the top surface of the cover l.

(13) A coat of the sealing compound is applied to the outer edge of thewasher 2l and so that the coat of seaiing compound extends aiso over thenearby portions of the lower surface of the cover 4.

(14) The cover I and the terminal 1 mounted thereon are then baked at atemperature between 220 F. and 240 F. forabot twelve hours.

We have found that when a terminal is constructed as above described andis mounted on a casing as shown in the drawing, and the aboveoutlinedtechnique is followed in preparing and assembling the parts, theconstruction is leakproof and will remain leak-proof even when thecasing and terminal are subjected to relatively high and lowtemperatures or when the casing and terminal are immersed in sait waterand the temperature of the water is changed over a relatively widerange. The sealing compound employed in making the structure andarrangement leak-proof must obviously be of such character that it wiilnot crack or fail to perform its seaiing function under the conditionsmet in service. A relatively high-temperature baking enamel may be usedas the sealing compound. A seaiing compound we have found to besatisfactory for the purpose is a mixture or a high-temperature bakingenamel and toluol in the proportions of 3.5 to 4 parts by volume ofenamel to one part of toluol.

What is claimed is:

A leak-proof terminal structure and arrangement coinprising incombination, an apertured wall coated on opposite faces with relativelysoft metal, seats formed in the coatings on said wall around theaperture in said wall, washers disposed on opposite sides of said walland resting in said seats, an insulating bushing, an enlarged upperportion on said bushing eXtendin above said washers. a reduced lowerportion on said bushing extending through said wall and said washers, aconducting rod extending longitudinally through said bushing, a flangeon said rod extending over the upper portion of said bushing, a washerlocated between said flange and the top of said enlarged upper portionOf said bushing, a collar supported on the lower portion of saidbushing, mans on said rod to hold the terminal parts in tlghtlyassembled condition and press the washers in said seats against saidseats, coats of moisture-proof seaiing compound covering the washers insaid seats and extending into leakproof seaiing engagement with saidwall and a coat of leak-proof sealing compound covering the washer onthe upper end of said bushing and extending into leak-proof sealingengagement with said bushinz and said flange.

ROBERT W. DE MONTE. LOUIS E. MILARTA.

